Load drive circuit and load drive system

Abstract

With a simple configuration, responsiveness between an electronic control unit and a load drive circuit is monitored without deteriorating characteristics of the load drive circuit. The load drive circuit according to the present invention diagnoses an abnormality in responsiveness of a switch element that drives a load based on a drive command of the switch element and a signal at an output terminal of the switch element.

The invention claimed is: 
     
       1. A load drive circuit comprising:
 a switch element that drives a load; 
 a diagnosis unit that diagnoses an abnormality in responsiveness of the switch element based on a drive command of the switch element and a signal at an output terminal of the switch element; and 
 an energization identification signal generating unit that compares a voltage at the output terminal of the switch element and a predetermined voltage threshold to discriminate whether or not the switch element is in an energization state or a cut-off state and output an energization identification signal representing the discrimination result, 
 wherein the diagnosis unit uses the energization identification signal to diagnose at least any one of a delay time between the drive command and the energization identification signal, an energization time of the switch element, or the number of times of energization of the switch element. 
 
     
     
       2. The load drive circuit according to  claim 1 ,
 wherein the diagnosis unit uses the energization identification signal to diagnose the switch element and uses the energization identification signal to determine whether or not a ground fault of the load occurs. 
 
     
     
       3. The load drive circuit according to  claim 2 , wherein in a cut-off period in which the drive command instructs the switch element to be in a cut-off state, the diagnosis unit uses the energization identification signal to determine whether or not the ground fault of the load occurs, and
 when it is determined that the ground fault of the load occurs in the cut-off period, the diagnosis unit determines that the switch element is abnormally energized. 
 
     
     
       4. The load drive circuit according to  claim 1 ,
 wherein the diagnosis unit uses the energization identification signal to diagnose the switch element and uses the energization identification signal to determine whether or not wiring for connecting the load drive circuit and the load is disconnected. 
 
     
     
       5. The load drive circuit according to  claim 4 , wherein in a cut-off period in which the drive command instructs the switch element to be in an energization state, the diagnosis unit uses the energization identification signal to determine whether or not the wiring is disconnected, and
 when it is determined that the wiring is disconnected in the energization period, the diagnosis unit determines that the switch element is abnormally energized in a period in which the wiring is not disconnected in the energization period. 
 
     
     
       6. The load drive circuit according to  claim 1 , wherein the load is configured as an electric load that opens and closes a fuel injection valve that injects fuel to an internal combustion engine,
 the drive command is a command for instructing the load to inject the fuel, 
 the drive command is a command for indicating an injection timing and an injection time of the fuel on the internal combustion engine in one combustion cycle, one or more times, and 
 the load drive circuit energizes the load so as to open and close the fuel injection valve according to the drive command. 
 
     
     
       7. The load drive circuit according to  claim 6 , further comprising a storage device that stores the diagnosis result obtained from the diagnosis unit,
 wherein the diagnosis unit stores the diagnosis result in the storage device every time the drive command indicates the injection timing and the injection time. 
 
     
     
       8. A load drive system comprising:
 the load drive circuit according to  claim 1 ; and 
 an electronic control unit that transmits the drive command to the load drive circuit. 
 
     
     
       9. The load drive system according to  claim 8 , wherein the electronic control unit includes
 a terminal that transmits the drive command to the load drive circuit, and 
 a communication interface that receives the diagnosis result obtained from the diagnosis unit from the load drive circuit. 
 
     
     
       10. The load drive circuit according to  claim 1 , further comprising:
 a terminal that receives the drive command from an electronic control unit that transmits the drive command; and 
 a communication interface that transmits and receives data to and from the electronic control unit, 
 wherein the diagnosis unit transmits the diagnosis result to the electronic control unit through the communication interface. 
 
     
     
       11. The load drive circuit according to  claim 1 , further comprising:
 a terminal that receives the drive command from an electronic control unit that transmits the drive command; and 
 a communication interface that transmits and receives data to and from the electronic control unit, 
 wherein the diagnosis unit transmits the diagnosis result obtained by using the energization identification signal to the electronic control unit through the communication interface. 
 
     
     
       12. The load drive circuit according to  claim 1 , wherein the diagnosis unit determines the number of times that the switch element is in an energization state,
 the diagnosis unit calculates a difference between the number of times that the drive command instructs the switch element to be in the energization state and the number of times that the switch element is in the energization state, and 
 when the difference does not fall within a predetermined determination threshold, the diagnosis unit outputs an abnormal flag indicating that the difference does not fall within the predetermined determination threshold. 
 
     
     
       13. A load drive circuit comprising:
 a switch element that drives a load; and 
 a diagnosis unit that diagnoses an abnormality in responsiveness of the switch element based on a drive command of the switch element and a signal at an output terminal of the switch element, 
 wherein after the drive command instructs the switch element to be in an energization state, the diagnosis unit determines whether or not a delay time until the switch element is in the energization state falls within a predetermined time window, and 
 when the delay time does not fall within the time window, the diagnosis unit outputs an abnormal flag indicating that the delay time does not fall within the time window. 
 
     
     
       14. A load drive circuit comprising:
 a switch element that drives a load; and 
 a diagnosis unit that diagnoses an abnormality in responsiveness of the switch element based on a drive command of the switch element and a signal at an output terminal of the switch element, 
 wherein the diagnosis unit determines a period in which the switch element is in an energization state, 
 the diagnosis unit calculates a difference or ratio between a time when the drive command instructs the switch element to be in the energization state and a time when the switch element is in the energization state, and 
 when the difference or ratio does not fall within a predetermined determination threshold, the diagnosis unit outputs an abnormal flag indicating that the difference or ratio does not fall within the predetermined determination threshold.